A known counterbore is described in DE No. 33 21 111 A1 or EP No. 129 116 A2. Reference is made to the disclosure contents of these two documents, inasmuch as the prior disclosures will be useful in understanding the present invention.
The characteristic of the known counterbore referred to above is the fact that the die heads or cutters comprise cutting edges that face in opposite directions, and are guided in receiving (take-up) slots in the cutter head, in such a way that they may be fixed in a set position and also moved or adjusted. The profile or cross section of the receiving slots is rectangular and penetrates, window-like, the external circumference of the cutting head, that is, constitutes a through bore on a diameter.